Cap measurement corner snap radius

CHANGELOG.md

@@ -10,6 +10,7 @@
 - UI: require the locked measurement target to be the frontmost normal pick before snapping, preventing hidden target geometry behind another part from receiving ruler endpoints.
 - UI: clear stale measurement snap status after cancelling a pending endpoint so the selected-object ruler returns to a neutral ready state.
 - UI: keep the measurement strip in Free pick status while Alt/Option previewing the backup free ruler path, even when the pointer is over empty canvas space.
+- UI: cap selected-object corner snapping by target edge scale so large grouped selections do not over-prioritize distant vertices when the pointer is closer to an edge.
 - Performance: cache selected-target measurement snap candidates while measuring so hover previews do not repeatedly rebuild vertex and edge lists for the same object.
 - Performance: validate selected-target measurement snap caches against target mesh signatures so transformed or updated geometry rebuilds snap candidates instead of reusing stale vertex and edge lists.
 - UI: restyle distance measurements as orthographic drawing-style dimension callouts with extension lines, arrowheads, and compact drafting labels instead of thick freehand ruler lines.

src/render/babylon/scene.ts

@@ -108,6 +108,7 @@ import {
   createMeasurementReading as buildMeasurementReading,
   createMeasurementState,
   createMeasurementTrianglesFromIndices,
+  createMeasurementVertexSnapRadius,
   drawMeasurementLabelCanvas,
   MEASUREMENT_LABEL_CANVAS,
   normalizeMeasurementUnit,
@@ -2039,7 +2040,7 @@ export class BabylonModelPreview implements WorkbenchPreview {
       vertices,
       edges,
       targetId,
-      vertexRadius: Math.max(size.x, size.y, size.z, 0.001) * 0.045,
+      vertexRadius: createMeasurementVertexSnapRadius(size, edges),
     };
     this.measurementSnapInputCache = input;
     this.measurementSnapInputCacheTargetId = target.uniqueId;

src/render/preview/measurement.test.ts

@@ -9,6 +9,7 @@ import {
   createMeasurementReading,
   createMeasurementState,
   createMeasurementTrianglesFromIndices,
+  createMeasurementVertexSnapRadius,
   createReferenceMeasurementScale,
   drawMeasurementLabelCanvas,
   formatMeasurementNumber,
@@ -176,6 +177,18 @@ describe("measurement helpers", () => {
     expect(snapped).toBeNull();
   });
 
+  it("caps the vertex snap radius by selected-target edge scale", () => {
+    expect(createMeasurementVertexSnapRadius(
+      { x: 10, y: 1, z: 1 },
+      [{ start: { x: 0, y: 0, z: 0 }, end: { x: 1, y: 0, z: 0 } }],
+    )).toBeCloseTo(0.1);
+    expect(createMeasurementVertexSnapRadius(
+      { x: 1, y: 1, z: 1 },
+      [{ start: { x: 0, y: 0, z: 0 }, end: { x: 1, y: 0, z: 0 } }],
+    )).toBeCloseTo(0.045);
+    expect(createMeasurementVertexSnapRadius({ x: 10, y: 1, z: 1 }, [])).toBeCloseTo(0.45);
+  });
+
   it("creates geometry snap edges from indexed and non-indexed triangles without face diagonals", () => {
     const squareVertices = [
       { x: 0, y: 0, z: 0 },

src/render/preview/measurement.ts

@@ -34,6 +34,8 @@ const UNIT_FACTORS_TO_METERS: Record<MeasurementUnit, number> = {
 const MIN_MEASUREMENT_SIZE = 1e-9;
 const MEASUREMENT_EDGE_KEY_SCALE = 1_000_000;
 const MEASUREMENT_COPLANAR_EDGE_DOT = 0.9995;
+const MEASUREMENT_VERTEX_RADIUS_SPAN_FACTOR = 0.045;
+const MEASUREMENT_VERTEX_RADIUS_EDGE_FACTOR = 0.1;
 
 export interface MeasurementSnapVertexCandidate {
   point: PreviewWorldPoint;
@@ -211,6 +213,27 @@ export function snapMeasurementPointToGeometry(
   };
 }
 
+export function createMeasurementVertexSnapRadius(
+  boundsSize: PreviewWorldPoint,
+  edges: readonly MeasurementSnapEdgeCandidate[],
+): number {
+  const span = Math.max(boundsSize.x, boundsSize.y, boundsSize.z, 0.001);
+  const spanRadius = span * MEASUREMENT_VERTEX_RADIUS_SPAN_FACTOR;
+  const edgeLengths = edges
+    .map((edge) => distanceMeasurementPoints(edge.start, edge.end))
+    .filter((length) => Number.isFinite(length) && length > MIN_MEASUREMENT_SIZE)
+    .sort((left, right) => left - right);
+  if (edgeLengths.length === 0) {
+    return spanRadius;
+  }
+
+  const referenceEdgeLength = edgeLengths[Math.floor(edgeLengths.length / 2)];
+  return Math.max(
+    Math.min(spanRadius, referenceEdgeLength * MEASUREMENT_VERTEX_RADIUS_EDGE_FACTOR),
+    MIN_MEASUREMENT_SIZE,
+  );
+}
+
 export function createMeasurementGeometryEdgesFromTriangles(
   vertices: readonly PreviewWorldPoint[],
   triangles: readonly [number, number, number][],

src/render/three/scene.ts

@@ -104,6 +104,7 @@ import {
   createMeasurementReading as buildMeasurementReading,
   createMeasurementState,
   createMeasurementTrianglesFromIndices,
+  createMeasurementVertexSnapRadius,
   drawMeasurementLabelCanvas,
   MEASUREMENT_LABEL_CANVAS,
   normalizeMeasurementUnit,
@@ -2752,7 +2753,7 @@ export class ThreeModelPreview implements WorkbenchPreview {
       vertices,
       edges,
       targetId,
-      vertexRadius: Math.max(size.x, size.y, size.z, 0.001) * 0.045,
+      vertexRadius: createMeasurementVertexSnapRadius(size, edges),
     };
     this.measurementSnapInputCache = input;
     this.measurementSnapInputCacheTarget = target;